藜麦内生细菌LS3发酵条件优化及其抑菌机制初探

Optimization of Fermentation Conditions and Inhibitory Mechanism of Endophytic Bacteria LS3 in Quinoa

藜麦黑茎病是危害藜麦的主要病害之一,可引起藜麦倒伏、籽粒空瘪和不育,严重影响藜麦籽粒的产量和品质。前期从藜麦穗中分离获得1株对藜麦黑茎病菌(Ascochyta caulina)具有良好抑菌活性的内生细菌,命名为LS3,为进一步开发应用该菌株,采用单因素试验法对LS3菌株的最佳培养基、碳源、氮源、温度进行筛选,对其发酵条件进行优化,采用鉴定培养基法对LS3菌株的抑菌活性物质进行检测,对其抑菌机制进行初探。结果表明,LS3菌株发酵所需最佳培养基为YSP培养基,最佳碳源为蔗糖,最佳氮源为牛肉膏+酵母粉,发酵最佳温度为28℃。对转速、装液量、接种量、pH以及发酵时间5个因素进行正交发酵优化,结合方差分析,并考虑成本因素,最终确定LS3菌株最佳发酵条件为:转速130 r/min,装液量150 mL/300 mL,接种量1%,pH值7.0,发酵时间96 h。对LS3菌株细胞壁降解酶活性检测发现,LS3菌株可分泌β-1,4-葡聚糖酶和胞外蛋白酶,但不能产生几丁质酶和β-l,3-葡聚糖酶。

Quinoa black stem disease is one of the main diseases that cause lodging,empty grain,and sterility,seriously affecting the yield and quality of quinoa grain.In this study,an endophytic bacterium with good antifungal activity against A.caulina was isolated from quinoa at the early stage and named LS3.In order to further develop and apply this strain.Single factor test was used to screen the optimal medium,carbon source,nitrogen source,and temperature of LS3 strain,the fermentation conditions were optimized.The antifungal activity substances of LS3 strain were detected using the identification medium method,the inhibitory mechanism was studied.The results showed that the best culture medium for LS3 fermentation was YSP medium,the best carbon source was sucrose,the best nitrogen source was beef paste+yeast powder,and the best fermentation temperature was 28℃.Through orthogonal test carried out on 5 factors-rotational speed,liquid volume,inoculation amount,pH,and fermentation time-combined with variance analysis and cost factors,the optimal fermentation conditions of the LS3 strain were determined to be:rotation speed 130 r/min,liquid loading 150 mL/300 mL,inoculation volume 1%,pH 7.0,and fermentation time 96 h.The activity of cell wall degrading enzyme of the LS3 strain was detected.It was found that the LS3 strain could secreteβ-1,4-glucanase and extracellular protease,but could not secrete chitinase andβ-l,3-glucanase.